Manufacture of nickel and cobalt salts



Dec. 2, 1947. A. H. DU ROSE MANUFACTURE OF NICKEL AND COBALI SALTS FiledJune 2, 1944 RATE OF sqLur/ow or SULFUR/ZED ELECTROSHEET xwcksz. //v 20pm 'CENT (By VOLUME) SULFUR/C ACID w m w w a PER CENT \SI-ILI-"IJR /NTHE METAL INVENTOR.

ARTHUR H. DU ROSE BY W 6% Patented Dec. 2, 1947 MANUFACTURE OF NICKELAND COBALT ALTS Arthur H. Du Rose, Eucld, Ohio, a signor to The HarshawChemical Company, Elyria, Ohio, a

corporation of Ohio Application June 2, 1944, Serial No. 538,436

6 Claims.

This invention relates to the manu acture of compounds of nickel andcobalt using nickel or cobalt metal or an alloy of nickel and cob-alt inmassive form as the source of nickel and cobalt. More specifically, theinvention is concerned with methods of preparing compounds from suchmetall c masses which are relatively pure so as to be difficultlysoluble in such acids, for example, as sulfuric and hydrochloric.

Nickel is available to the market in various forms adapted to thepractice of the pre ent invention. including various forms of scrapmetal principally cons sting of nickel and especia'ly a highly pure formof nickel known as electrosheet which is recovered from nickel ores byelectrolytic processes. Such materials have been found to dissolve inordinary, aqueous solutions of acids, such as sulfuric and hydrochloric,at a rate too low to be satisfactory. As a result, attempts have beenmade to speed up the solution by the use of current, blowing with air,etc. These procedures, although more or less successful, areobjectionable in respect to cost and present various equipmentdiificulties which have discouraged their use.

I have now discovered that the relatively pure forms of nickel as wellas cobalt, nickel-cobalt alloys, and alloys with other metalsprincipally composed of nickel or cobalt, can be dissolved much morereadily in such acids as sulfuric, hydrochloric, nitric, acetic andformic, if they are first sulfurized'. Sulfurization may take the formof heating the massive metal with a suitable sulfurizing agent. It is,of course, possible to melt the metal with the sulfurizing agent andthereby introduce a sufiicient quantity of sulfur, but I find that thisis not necessary to the result and a much cheaper method ofsulfurization can be employed,

In the drawing, the figure is a graphical representation of therelationship between the amount of sulfur in the metal and the rate ofsolution in sulfuric acid expressed in. grams dissolved per square footper hour.

The introduction of sulfur into the metal may be accomplished, as aboveindicated, by meling the metal with sulfur, or it may be accomplishedbyheating the metal in massive form with a sul-' fu-rizing agent. Again,it may be accomplished by co-electrodepositin the metal with a suitablesulfurizing agent by including such sulfurizing agent in theelectrodeposition bath whereby it will be codeposited and thenfollowingv this by heat treating the resulting deposit. It will not benecessary to describe the procedure for incorporae tion of sulfur bymelting the metal with sulfur or suiable sulfur compound, since that isa metallurgical procedure within the skill of the art and can beaccomplished by any metallurgist skilled in the art of working nickel.Special procedures for sulfurizing by heating the massive metal with asulfurfzing agent, and special procedures for incorporating sulfur intothe metal by co-electrodeposition and heat treatment will now be descrbed.

The introduction of sulfur into the metal by heating the massive metalwith a sulfurizing agent below the melting point of the metal massdepends upon several variables, temperature, time, pressure,concentration of the sulfurizing agent, and the nature of thesulfurizing agent. In general, the massive metal is heated in OOH-.-tact with the sulfurizing agent whereby the sulfur or sulfur compound iscaused to diffuse into the metal. In selecting a set of conditionssuitable for this type of sulfurization, I prefer to employ a pressurenot much above atmospheric because such low pressures require arelatively less complicated and expensive type of equipment. I prefer touse a gaseous sulfurizing agent, such as HzS, sulfur vapor, carbonbisulfide vapor, sulfur chloride vapor, or S02 plus a reducing gas.These may be diluted with nitrogen or other inert gas for the purpose ofcontrolling the introduction of sulfur into the electro-sheet.

While I prefer to use a gaseous sulfurizing agent as indicated, I mayuse various non-gaseous agents. I may, for example, dip the massivemetal, such as electro-sheet nickel, into a solution of sulfur in carbonbisulfide whereby a sulficient amount of sulfur will be caused to adhereto the surface of the sheet, and then by heating the so-treated sheet Iam able to cause sulfur to be diffused through the metal. Again, I maydip the nickel mass in sodium polysulfide solution or in varioussolutions or emulsions of sulfur in liquid carriers. In each case thesulfur-containing coating is applied and the metal is then heated at atemperature suflicient to Cause-the sulfur to migrate into the metal.Such heating will be, in general, well below the melting point of themetal mass. Heating, in general, will be continued sufficiently to causethe sulfur to diffuse substantially uniformly through the mass ofmet'al.The advantages of the invention may berealized to some extent withoutheating for a sufficient time to cause the sulfur to become homogeneously distributed throughout, but in gen-- eral it is desirable toheat long enough to secure t result; I

It is possible, also, to contact the metallic mass with finely dividedsulfur by placing in a furnace a layer of metal and a layer of sulfur,another layer of metal, etc., and then heating the furnace charge tocause the sulfur to be absorbed into the metal. The amount of sulfuremployed may be regulated so as to give the desired final result and theheat treating continued until the sulfur is sufficiently diffusedthrough the metal. Preferably, such treatment would result in vaporizingthe sulfur and so would be equivalent to the use of a gaseoussulfurizing agent, but a portion of the treatment might be carried outbelow the boiling point of sulfur.

The term sulfur when used herein to describe the composition of thetreated metal is to be read as including elemental sulfur and combinedsulfur, that is, sulfur compounds, it being my belief that sulfur ispresent in the treated metal at least partially in the form of the metalsulfide, but possibly to some extent as elemental sulfur or the compoundused as the sulfurizing agent. The term sulfurizing agent includes HzS,sulfur vapor, solutions of sulfur in liquids, emulsions and othersuspensions of sulfur in liquids, solid or liquid sulfur, carbonbisulfide, sulfur chloride (S2012), S02 with a reducing gas, heavy metalsulfides (e. g., sulfides of copper, lead, iron, nickel, cobalt,manganese), and mixtures of such of these as may be in gas or vaporphase with inert gases such as nitrogen.

Having selected a suitable sulfurizing agent, I treat sample pieces ofthe metal to be treated for various lengths of time and then test themfor sulfur content. I select a time of treatment such as will introducethe desired percentage of sulfur under the selected conditions oftemperature and pressure. I prefer to introduce at least .01% of sulfurinto the metal. This percentage is determined by analyzing for elementalsulfur. It is desirable to introducefrom .02 to .1% of sulfur (elementalsulfur based upon the weight of the metal) and a greater amount, forexample, or 2% can be used, but is not necessary. This will be apparentby reference to the draw-- ings which indicate a very good solution rateat .02% and very little increase as a result of use of large percentagesof sulfur.

It will be noted that the individual determinations indicated on thedrawings by small circles do not fall upon a sharply defined curve butdo fall Within a clearly defined area. The reason for this is that thereis very substantial individual variation in the determinations which Ibelieve is explained by the existence of a fairly large experimentalerror. This experimental error arises from (1) variation due to the factthat the metal dissolved in the solubility test and the metal analyzedchemically for sulfur content could not be the same, and (2) variationdue to inability to measure the actual surface exposed which varies fromthe apparent surface on account of small irregularities.

Havingdetermined the optimum conditions for introduction of the selectedamount of sulfur, I proceed to follow these conditions in the treatmentof the metal or alloy to be treated, after which such metal is dissolvedin sulfuric acid or hydrochloric acid or another of the acids mentionedabove depending upon the compound to be made. I find that the solutionrate is quite Satisfactory when from 02% to .1% of sulfur has-beenintroduced as is clearly indicated in the drawing.

Heat treating will normally be a separate p from the step of absorbingthe sulfur into the metal, but obviously it is possible to overlap orcombine the two steps by placing a predetermined amount of thesulfurizing agent and the body of metal in a heating furnace or oven andelevating the temperature to the desired degree.

Normally the absorbing step will be carried out at a temperature of theorder of 300 C. to 700 C. for a few minutes, say one to ten minutes, andthen the supply of sulfurizing agent will be cut off and the temperaturewill be raised to from 600 C. to 1000" C. and held there from a quarterhour to five or even ten hours to thoroughly diffuse the sulfurthroughout the plate, or continued heating at 500 C. (after stopping thefiow of sulfurizing gas) for two to 24 hours. After diffusion of thesulfur, the metal may be air cooled, furnace cooled, water quenched, oracid quenched.

It may be desirable, instead of melting the sulfur with the metal or ofintroducing it by heating with a sulfurizing agent below the meltingpoint of the metal, to introduce the sulfur by co-electrodepositing asulfur compound with the metal and then heat treating. This might bedone in connection with the electrolytic recovery of nickel or cobalt bysimply including a suitable sulfur compound in the solution from whichthe electro-sheet is deposited.

I am aware that co-electrodeposits have been made from solutionscontaining sulfur compounds and resulting in the inclusion to a smallextent of such sulfur compounds in the deposit. For example, in thedeposition of nickel in brilliant form for ornamental purposes, it iscommon to make use of a sulfur-containing compound such as a naphthalenesulfonic acid, and this does result in the inclusion of a small amountof the sulfur compound in the deposit. Such deposits. however, even ifit were attempted to use them as a source of metal to be dissolved forthe formation of nickel compounds, would not prove satisfactory in viewof, the nature of the deposit. I have found that in makingco-electrodeposits from electroplating solutions containing sulfurcompounds, the sulfur compounds are laid down in layers. There thusresults a layer which is diflicult to dissolve because it containsinsuificient sulfur, followed by a layer which contains more sulfur thanis necessary. The result is that the solution rate of co-deposits thusformed is relatively low. I have found, however, that if a deposit somade is heat treated, the sulfur becomes diffused and substantiallyhomogeneously distributed and the solution rate is increased to asatisfactory level.

In preparing electrodeposits of nickel or cobalt for solution in acidsto form the corresponding compounds, I may make use of any of variouselectroplating solutions, including therein a suitable source of sulfur,such as thiourea, sodium thiosulfate, saccharine, various aromaticsulfonic acids, such as the benzene and naphthalene sulfonic acids andtheir sodium, nickel and cobalt salts. Various other soluble sulfurcompounds capable of co-depositing with metal may be employed. While theinclusion of sulfur in the deposit results in some improvement in therate of solution without the heat treating step, I have observed that byheat treating at relatively low temperatures and for relatively shortperiods of time, I am able to more than double the solution rate. Iattribute this mainly to the breaking down of the laminar structure ofthe electrodeposit, and it may also be due in some degree to the 5,breaking down of; the sulfur compound used; the plating solution toasimpler compound Qrto, the reaction of: such compound with the metal toform a, metal sulfide. I preferto. makeuse of plating solutionscontaining such quantities. of sulfur compounds asto result in theinclusion in the. electrodeposit of at least 01%: of sulfur cal-.culated as elemental sulfur, and preferably from 02% to. 1%. I do notmean to imply that the sulfur is necessarily present in the deposit aselemental sulfur but only that the sulfur com-. ponent of whatevercompound is there present amounts to the percentages indicated.

Heat treatment of the electrodeposit should include heating at atemperature from 250 C. to 13009 C. for a time sufiicient to causesubstantial diffusion of the sulfur whereby to increase the solubilityin sulfuric, hydrochloric, nitric, ace tie and formic acids. This can beaccomplished in as little as one minute at 1300- C. but may requireasmuch as 30 minutes at 250C. Longer heatingtimes are advantageousespecially at, the w r emn r tu s.

The following examples will serve to illustrate the invention:

Example I A body of electro-sheet nickel was exposed to; a

mixture of one part H2S and parts nitrogen.

by volume. The temperature was 600 C., the pressure only slightlyelevated above atmospheric, and the time was 3 minutes. The body wasthen heat treated at 800 C. for one hour to diffuse the sulfur, thenitrogen flow being continued throughout the heat treatment to an extentsufficient to prevent oxidation. That is, the atmosphere in the heattreating furnace was non-oxidizing throughout the treatment. Theresulting body contained approximately 0.13% sulfur and when introducedinto 35% (by vol ume) sulfuric acid at boiling temperature exhibited asolution rate of approximately 148 grams per square foot of apparentsurface per hour. (The surface was approximately fiat but rough and noattempt was made to measure the increase of surface due to roughness.The apparent surface was used. Numerous similar determinations were madewith electro-sheet nickel sulfurized by means of HzS, using aqueoussulfuric acid as the solvent. These are plotted in the drawing.)

Example II A body of electro-sheet nickel was placed in a combustiontube with a combustion boat containing sulfur chloride ($2012). Thetemperature was 600 C. and nitrogen was passed through the tube so as tovaporize the sulfur chloride and bring it into contact with theelectro-sheet nickel. This treatment was continued for hour and then thetemperature was raised at 800 C. for one hour. The resulting nickelanalyzed .24% sulfur and dissolved very readily in both sulfuric andhydrochloric acid, approximately 60 grams per square foot of apparentsurface per hour in 20% (by volume) sulfuric acid.

Example III A small piece of electro-sheet nickel was packed in leadsulfide in a crucible and heated for one hour at 750 C. The nickelanalyzed .007% sulfur and showed increased solubility in both sulfuricand hydrochloric acid as compared to pure electro-sheet. In a similarcase, using copper sulfide instead of lead sulfide, the nickel 6.nalyzed: -Q su fur nd; dissol ed in. sulfuric. and; hydrochloric. acid-1more readilythan pure; electroesheetnickel. (Solution; rate. was. not.-quantitatively determined):

Ex mp e V A nickel. pl tin olut on conta nin .90. r ms of m 1 sulfate.NiSQiGHZQ 0- eram p r:

liter; of ni el hloride N C1a6H2Ol. 37-5 rams. per; iter bor cacid. H303)... 4.. crl ter of formi acid. and. ne. ram. per lit r of. thi rea.remainde wateuwas used} to p oduc anelectr deposit. The depositwasfound.to contain 0.5 4%. sulfur}. Before heat; tr atment, this deposit.dissolvedin; 2.0% (by. volume) sulfuric acid at the; rate; of" 110 gramsper square foot perhour. After heating at 700 C. for A; hour, thesolution rate. in the same acid had increased to. 2811 grams per squarefoot. per hour. This compares with a solutionrate. of- 4 to. 8 grams persquare. foot per hourin the case of untreated nickel electro-sheet.

that used in Example IV' contained 2 grams per liter: of saccharine inplace of the thiourea ofExample This'deposit analyzed 028% sulfur, andbefore heat treatment had a solution rate of 22 grams persquare foot perhour in 20% (-by' volume) sulfuric acid. Afterheating at 700"" C. foahouuthe solution rate had increased to 52 grams per square foot perhourin the same acid.

Having thus described my invention, what I claim is:

1. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such'bodyin contact with a sulfurizing agent of the class consisting of hydrogensulfide, sulfur, carbon'bisulfide, sulfur chloride, sulfur dioxide witha reducing gas, and the sulfides of copper, lead, iron, nickel, cobaltand manganese and mixtures of such materials, the temperature of heatingbeing at least 300 C. and being continued for a sufficient time tointroduce from .01% to 2% of sulfur, calculated as elemental sulfur,into the metallic body and to diffuse the same therethrough, and thendissolving the resulting sulfurized metallic body in an acid of theclass consisting of sulfuric, hydrochloric, nitric, acetic and formic.

2. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such bodyin contact with hydrogen sulfide, the heating being carried out between300 C. and 700 C. for a sufficient time to introduce from .01 to 2% ofsulfur, calculated as elemental sulfur, into the metallic body and todiffuse the same approximately evenly throughout, and then dissolvingthe resulting sulfurized metallic body in an acid of the classconsisting of sulfuric, hydrochloric, nitric, acetic and formic.

3. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such bodyin contact with sulfur, the heating being carried out between 300 C. and700 C. for a suiiicient time to introduce from .01 to 2% of sulfur,calculated as elementalsulfur,

into the metallic body and to difiuse thesameapproximately evenlythroughout, and then dissolving the resulting sulfurized metallic bodyin an acid of the class consisting of sulfuric, hydrochloric, nitric,acetic and formic.

4. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such bodyin contact with a mixture of an inert gas and hydrogen sulfide, theheating being carried out between 300 C. and 700 C. for a suflicienttime to introduce from .01 to 2% of sulfur calculated as elementalsulfur into the metallic body and to diffuse the same approximatelyevenly throughout, and then dissolving the resulting sulfurized metallicbody in sulfuric acid. a

5. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such bodyin contact with a sulfurizing agent of the class consisting of hydrogensulfide, sulfur, carbon bisulfide, sulfur chloride, sulfur dioxide witha reducing gas, and the sulfides of copper, lead, iron, nickel, cobaltand manganese and mixtures of such materials, the heating beingcontinued at high enough temperatures and for a sufficient time tointroduce from .01 to 2% of sulfur, calculated as elemental sulfur, intothe metallic body, thereafter bringing the temperatureto at least 600 C.for at least 15 minutes to diffuse the sulfur through said body, andthen dissolving the resulting sulfurized metallic body in an acid of theclass consisting of sulfuric, hydrochloric, nitric, acetic and formic.

6. In the manufacture of compounds of nickel and cobalt from the metal,the steps of sulfurizing a body of metal of the class consisting ofnickel and cobalt and alloys of nickel and cobalt by heating such bodyin contact with a sulfurizing agent of the class consisting of hydrogensulfide, sulfur, carbon bisulfide, sulfur chloride, sulfur dioxide witha reducing gas, and the sulfides of copper, lead, iron, nickel, cobaltand manganese and mixtures of such materials, the temperature of heatingbeing at least 300 C. and being continued for a sufficient time tointroduce from REFERENCES CITED The following references are of recordin the file of this patent:

Carpenter and Robinson, Metals, vol. II, page 1386. Published by OxfordUniversity Press, London,-New- York, and Toronto (1939).

